03/24/2006
SARS Epidemic: 2003
credit 1: http://www.guardian.co.uk/gallery/image/0,8543,-10704826770,00.html
credit 2: http://www.teslasociety.com/sars2.jpg
As you read the articles listed for the next class on Avian Flu (listed below), think about how we should respond to the potential crisis. By we, I mean
you personally
the US Government
the world as a whole
Readings:
Web: Avian Flu: Assessing the Threat- a very long document; skim, don't print.
WebCT
readings:
Other Diseases
How Advanced Preparation Can Help
Using a computer program called Episim, Barrett et al. have recently simulated the effects of an intentional release of small pox virus in Portland, OR. Two scenarios were run, one without a response, the other with targeted target vaccination and quarantine on Day 14 of simulated smallpox attack. The results are shown below. They plan to have finished a similar simulation of an avian flu epidemic in April
Scientific American. March 2005, pg 60
From where are diseases emerging?
A recent map created by Peter Daszak of the Consortium for Conservation Medicine at Wildlife Trust shows where diseases have emerged over the last 40 years. Contrary to notions that new disease causes arise in Africa (examples HIV, Ebola Virus), he has found that most originate in "Western" societies. These include diseases arising from antibiotic-resistant germs and travel. A report published in the New England Journal of Medicine (April 6, 2005) shows more startling news. Conservation medicine suggests stands on the principle that the relationships among humans, animals, and the ecosystem as a whole is a determinant of the balance between health and disease. Human activities which alter this balance will lead to emerging diseases in both humans and animals. Mad Cow
Insert: Figure from
Science, Vol 307, Issue 5713, 1190 , 25 February 2005
(permission pending; Submission Number # 30272 )
Antibiotic-resistant Staph infections are on the rise.
A report in the April 7, 2005 NEJM shows that antibiotic-resistant staph infections, which were thought to arise mostly in hospitals, are increasingly rising in the community as a whole. About 17 percent now arise in the community (20 percent in Atlanta, 12 percent in Minnesota and 8 percent in Baltimore). In addition, the Staph bacteria acquired "flesh-eating" (also called necrotizing fasciitis) characteristics" found most usually in certain Strep bacteria. (
What causes necrotizing fasciitis?
"Three streptococcal toxins, formerly known as Erythrogenic toxin, are recognized: types A, B, C. These toxins act as superantigens. As antigens, they do not requiring processing by antigen presenting cells. Rather, they stimulate T cells by binding class II MHC molecules directly and nonspecifically. With superantigens about 20% of T cells may be stimulated (vs 1/10,000 T cells stimulated by conventional antigens) resulting in massive detrimental cytokine release. SPE A and SPE C are encoded by lysogenic phages; the gene for SPE B is located on the bacterial chromosome.
"The erythrogenic toxin is so-named for its association with scarlet fever which occurs when the toxin is disseminated in the blood. Re-emergence in the late 1980's of exotoxin-producing strains of S. pyogenes has been associated with a toxic shock-like syndrome similar in pathogenesis and manifestation to staphylococcal toxic shock syndrome, and with other forms of invasive disease associated with severe tissue destruction. The latter condition is termed necrotizing fasciitis. Outbreaks of sepsis, toxic shock and necrotizing fasciitis have been reported at increasing frequency. The destructive nature of wound infections prompted the popular press to refer to S. pyogenes as "flesh-eating bacteria" and "ski-eating streptococci". " http://textbookofbacteriology.net/streptococcus.html